I can't speak to that either way (I haven't done a manual installation in a long time) but setting

  d-i passwd/root-login boolean false

in a preseed file seems to still work just fine (to skip "creation" of a root account).

The "sudo" package will be installed and the user created during installation will be added to the "sudo" group.

Good to know, thanks. Note that you'll be locked out of rescue/emergency with that, unless you also modify the unit file for (one or both of) them.